MED1003 Molecules, Cells, and Genes Lecture Notes PDF

MED1003 Molecules, Cells and Genes by Siu Wai (Phyllis) TSANG, PhD TUNG WAH COLLEGE email: [email protected] Office#: 3190-6713 Prepared by SWT 2024 email: [email protected] 1 Study of the Ce...

MED1003 Molecules, Cells and Genes by Siu Wai (Phyllis) TSANG, PhD TUNG WAH COLLEGE email: [email protected] Office#: 3190-6713 Prepared by SWT 2024 email: [email protected] 1 Study of the Cell From the single cells that make up the most basic organisms to the trillions of cells that constitute the complex structure of the human body, each and every living being on Earth is composed of cells The discovery of the cell would not have been possible if not for advancements to the microscope Prepared by SWT 2024 email: [email protected] 2  http://www.public-domain-image.com/ http://www.antique-microscopes.com http://www.microscopy-uk.org.uk Prepared by SWT 2024 email: [email protected] 3 Different microscopes Light microscope or Compound microscope Optical microscope 光學顯微鏡 Light microscope (bright / dark field) https://microscopeinternational.com/content/resources/compound-microscope-labeled.jpg Phase contrast microscope Fluorescence microscope Confocal microscope Electron microscope 電子顯微鏡 Transmitted electron microscope Scanning electron microscope Prepared by SWT 2024 email: [email protected] 4 Brightfield microscopy The light source and detection objective are placed on opposite sides of the sample The sample is imaged by its effect on the light passing through it, i.e., illumination Most cells are thin and transparent, they do NOT absorb much light and so are difficult to see without adding optics might see nothing more than vague outlines Prepared by SWT 2024 email: [email protected] 5 Darkfield microscopy The system comes with an extra opaque disc underneath the condenser lens  central blacked-out area The light coming from the source cannot directly enter into the objective The light strikes the sample at an oblique angle The specimen is brightly illuminated on a dark background Prepared by SWT 2024 email: [email protected] 6 Phase contrast microscopy An optical microscopy technique used to enhance the contrast of images of transparent and colourless specimens It is majorly used for observing specimens that have not been killed, fixed or stained and are in their natural state You may experience the difference between a brightfield image and a phase contrast image using the link below https://www.leica-microsystems.com/science-lab/microscopy- basics/phase-contrast-and-microscopy/ Prepared by SWT 2024 email: [email protected] 7  http://zeiss-campus.magnet.fsu.edu/articles/basics/images/fluorescencefigure6.jpg Prepared by SWT 2024 email: [email protected] 8 Magnification Most compound microscopes come with interchangeable lenses known as objective lenses Objective lenses come in various magnification powers, e.g., 4×, 10×, 40×, and 100× Magnification of the eye-piece (ocular) varies between 5× and 30×, e.g., commonly used 10× Total Magnification = eye-piece x objective e.g., Objective lens magnification: 10× Eye-piece magnification: 10× Total magnification = 10× x 10× = 100× Prepared by SWT 2024 email: [email protected] 9 Fluorescent microscopy British scientist Sir George G. Stokes first described fluorescence in 1852 He observed that the mineral fluorspar emitted red light when it was illuminated by ultraviolet excitation Until the 1930s, the use of fluorochromes was initiated in biological investigations to stain tissue components, bacteria and other pathogens https://www.rp-photonics.com/img/kahn_fl_image.jpg Biological fluorescent stains are used DAPI and Hoechst bind to the minor groove of DNA, when excited by UV light, they give a blue color  highlighting the nuclei of cells Prepared by SWT 2024 email: [email protected] 10 Immunofluorescence The highly specific binding of an antibody to its antigen, thereby labelling specific proteins or other molecules within the cell  immunofluorescence For example, Use a primary mouse antibody against insulin Use a secondary antibody against mouse that derivatized with a green fluorophore ofluorescence/IF_principle_direct_indirect.jpg https://ibidi.com/img/cms/applications/immun Green = presence of insulin in the cell Prepared by SWT 2024 email: [email protected] 11 Confocal microscopy Confocal microscopy produces 3-D images of the specimen fferences-between-wide-field-confocal-and-multiphoton-microscopy-approaches-a.png Suleiman/publication/299444264/figure/fig2/AS:614318466932750@1523476344437/Di https://www.researchgate.net/profile/Hani- Specimen in confocal microscopy and two-photon microscopy are stained with fluorescent dyes Two-photon microscopy can give a deeper tissue penetration and less phototoxic to the sample, but requires higher power Prepared by SWT 2024 email: [email protected] 12 Prepared by SWT 2024 email: [email protected] 13 Electron microscopy Prepared by SWT 2024 email: [email protected] 14 Prepared by SWT 2024 email: [email protected] 15 Summary Fluorescent / confocal microscopes or other optical microscopes use a series of lenses and mirrors to focus the laser light (or visible light) onto a specific plane within the sample, which is then scanned to produce an image Electron microscopes scan the sample using a beam of electrons instead of a beam of light to produce an image have much higher range of magnification have much higher resolution Prepared by SWT 2024 email: [email protected] 16  https://ib.bioninja.com.au/_Media/light-vs-electron_med.jpeg Prepared by SWT 2024 email: [email protected] 17  Cell structure Kahoot! Game https://kahoot.it/solo/?quizId=5fd1215f-b824-48db-80dd-885f915f82b5 Prepared by SWT 2024 email: [email protected] 18